Field of the Invention
The present invention relates to a light scanning apparatus which is particularly suitable for use in an image forming apparatus such as a laser beam printer, digital copying machine, and multi-function printer.
Description of the Related Art
There have been developed various light scanning apparatuses for color image forming apparatuses that form color images by superposing images of multiple colors. Japanese Patent Application Laid-Open No. 2009-103816 discloses a light scanning apparatus having stops as many as a plurality of light sources and employing a technique of spacing the stops apart from a polygon mirror to reduce light causing ghost images or increasing the oblique incidence angle of light fluxes on a deflector. Japanese Patent Application Laid-Open No. 2009-3124 discloses a light scanning apparatus having stops (or irises) as many as a plurality of light sources and employing a technique of arranging the stops at appropriate locations to facilitate separation of optical paths in a scanning optical system.
However, in cases where a system in which each of the plurality of light sources has a plurality of light emission points (multi-beam system) is employed, the plurality of light emission points are arranged with spacing between each other with respect to the main scanning direction. Consequently, the positions at which the principal rays of the light fluxes emitted from the plurality of light emission points are incident on the deflection surface of the polygon mirror are largely spaced apart from each other along the main scanning direction. Therefore, if a multi-beam system is employed in the apparatuses disclosed in Japanese Patent Application Laid-Open No. 2009-103816 and Japanese Patent Application Laid-Open No. 2009-3124, there arise a problem that the size of the deflector cannot be made small and a problem that a displacement of the focus position with respect to a scanned surface leads to a displacement of the positions of incidence of light fluxes on the scanned surface in the main scanning direction (main-scanning jitter), thereby deteriorating the image quality.
The present invention is intended to provide a light scanning apparatus that allows reduction of main-scanning jitter and size reduction of a deflector while using a plurality of light sources each having a plurality of light emission points.